The present invention relates to an optical information recording method and an optical information recording device which form mark by irradiating light on a record medium and records information.
There is a phase change type optical disk which performs recording by using a phase change between a crystal and an amorphous caused by thermal as one of an optical record medium in which light is irradiated thereon, thereby a mark capable of optically being identified is formed by thermal generated therefrom, and is recorded. The record film of the phase change type optical disk is a crystal in a steady state. However, a region where the light is irradiated gives rise to the phase change to the amorphous by being cooled after heated and melted. An information can be recorded by forming an amorphous part as a mark by using this principle. In such a phase change type optical disk, a PWM (Pulse Width Modulation) method which makes correspondence to binary information which records the position of beginning and termination of the mark is effective to improve the record density.
In general, when a long mark is formed to decrease a thermal storage effect according to the irradiation of light in a case that the PWM scheme is applied to the optical disk, a so-called multi-pulse is recorded by using a divided plurality of optical pulses not a single optical pulse as the irradiation light. An example of such a multi-pulse record is shown in FIG. 1A and FIG. 1B. FIG. 1A and FIG. 1B are examples when information is recorded by {fraction (8/16)} modulation code, and the mark length becomes a discrete value of 3T to 14T for record window width T.
According to FIG. 1A and FIG. 1B, the short mark of 3T in length (hereinafter, mark of 3T in length is called xe2x80x9cshort markxe2x80x9d for convenience sake about the explanation) which is the shortest mark is recorded by the single pulse of 1.5T in width as shown in FIG. 1A. However, the long mark of length 4T or more (hereinafter, length 4T or more mark is called xe2x80x9clong markxe2x80x9d for convenience sake about the explanation) has the period when only the amount of long or more than 3T mark repeats a peak power level period of 0.5T and an erasing power level period of 0.5T after. a leading pulse of width 1.5T shown in FIG. 1B. That is, when the long mark is recorded, the following pulse of 0.5T in width is added and formed, and the pulse width (time from start of a leading pulse to the end of the following final pulse in case of the multi-pulse) to form the mark increases T when the recorded mark length increases to T more than the shortest mark length.
However, there is a disadvantage in which the position of the beginning and the termination of the mark actually formed changes from the planned position depending on the length of the mark length even if such a multi-pulse is recorded. The beginning position and the termination position shift in a direction where the long mark is shortened compared with the short mark as for the formed mark, even when the irradiation starting or the irradiation completion of a light pulse is performed according to the same timing as shown from FIG. 2A in FIG. 2C for example according to only the mark length and the length at mark intervals.
That is, when the irradiation of light is started on the same timing when the short mark and the long mark are formed, both of them become the same heating condition until the leading pulse irradiation is completed. When a short mark which uses only a leading pulse is formed, the region where the medium is heated and melted is cooled as it is and becomes an amorphous. The beginning position of the mark shifts in the direction where the mark length is shortened, since the region which is heated and melted by a leading pulse receives re-heating by the irradiation of the following pulse, and the re-crystallization in the peripheral section of an amorphous region is accelerated when the long mark which uses the multi-pulse record is formed.
On the other hand, when an optical irradiation is completed when the short mark and the long mark are formed at the same timing, both of the temperature distributions when an optical irradiation is completed by a thermal characteristic of the medium are not always the same. The reason is as follows. The medium temperature immediately after heating by the following pulse lowers more than the medium temperature immediately after heating by a leading pulse when the long mark is formed. Therefore, a melted region of the optical irradiation end becomes small. As a result, the termination position of the mask shifts in the direction where the mark length is shortened as for the long mark.
The beginning position and the termination position of the long mark shift in the direction where the mark length is shortened more than the beginning position and the termination position of the short mark like this. It becomes necessary to perform some record compensation to avoid the shift of the beginning position and the termination position of the mark according to the mark length, and to accurately form the mark. As this record compensation method, a method of forming the mark by moving the leading pulse and the final pulse positions of the irradiation light pulse beforehand according to the length of the mark which intends to be formed is proposed.
However, it is necessary to change and generate an optical pulse from the clock synchronization state in this record compensation method, and it is necessary to change the amount of the change (that is, amount of the move at the position of the leading and the end by the length of the mark) according to the mark length. The disadvantage in which coexisting of accuracy and the cost becomes difficult occurs, since a complex circuit like the programmable delay line is needed.
As mentioned above, in the conventional record compensation method by which the position of the leading and the end of the irradiation light pulse is moved and generated beforehand according to. the length of the mark and the mark is formed to avoid the shift of the beginning position and the termination position of the mark according to the length of the mark and to form the mark in accuracy, there is a disadvantage that a complex circuit is necessary to change the amount of the change and it is difficult to make the accuracy of the formed mark and the cost united, by the change of an optical pulse from the clock synchronization state and the occurrence according to the mark length,.
Therefore, an object of the present invention is to provide an optical information recording method and the optical information recording device which have the record compensation method by which the accuracy of the mark formed without accompanied by a big cost increase is enabled to be improved.
Another object of the present invention is to provide an optical information recording method and an optical information recording device which have the compensation method for the record which can improve the position accuracy of the mark formed even when the line record density is different.
An optical information recording device according to the present invention forms a mark, in which the mark indicating record information is formed by irradiating a record light pulse on a record medium, by controlling a strength of the record light pulse according to both of a mark length of the mark and a record density in a mark length direction of the record medium.
Another optical information recording device according to the present invention forms a mark, in which the mark indicating record information is formed by irradiating a record light pulse on a record medium, by controlling a pulse width of the record light pulse according to both of a mark length of the mark and a record density in a mark length direction of the record medium.
Still another optical information recording device according to the present invention forms a mark, in which the mark indicating record information is formed by irradiating a record light pulse on a record medium, by controlling a strength of the light and a pulse width of the record light pulse according to both of a mark length of the mark and a record density in a mark length direction of the record medium.
Preferred manners of the present invention are as follows.
(1) The record light pulse includes at least one of a monopulse which has a width corresponding to the mark length, and a multi-pulse which has a plurality of pulses according to a number of pulses corresponding to the mark length. Where, a strength of the record light pulse after irradiation of the monopulse or the multi-pulse is lower than a strength necessary to erase the mark. The multi-pulse includes a plurality of pulses and a strength of the multi-pulse between each of the plurality of pulses is lower than a strength necessary to erase the mark.
(2) The record light pulse has a first light pulse, which is a monopulse corresponding to the first mark length, to form a first mark having a first mark length shorter than a predetermined length, and a second light pulse, which is a multi-pulse which consists of a plurality of pulses according to a number of pulses corresponding to the second mark length, to form a second mark having a second mark length longer than the first mark length of the first mark.
(3) The record light pulse has a first record light pulse to form a first mark having a first mark length shorter than a predetermined length and second record light pulses to form a second mark having a second mark length longer than the first mark length, and a strength of the first record light pulse is lower than a strength of a part of the second record light pulses.
(4) A strength of the record light pulse to form a mark having a predetermined mark length is lowered with increasing a record density in the mark length direction.
(5) A pulse width of the record light pulse to form a mark having a predetermined mark length is shortened with increasing a record density in the mark length direction.
(6) The record light pulse has a plurality of record light pulses and the plurality of record light pulses differ from each other.
(7) Especially, it is suitable for an optical information recording method to which the record film is changed from the crystal to the amorphous by thermal, and the mark is formed with the irradiation light by using the medium which has the record film of the phase change type as a record medium.
As for the optical information recording method according to the present invention, in that case, it is possible to achieve of course as a device to execute the method, and the optical information recording device has the means (element) to execute the method. It is desirable that an optical information recording device has a register storing an irradiated light strength information and a pulse width information, and at least one of the optical strength and the pulse width by replacing this optical strength information temporarily stored to the memory means and the pulse width according to the record density in the mark length direction of the record medium.
According to the present invention, The shift of the beginning position and the termination position of the mark is reduced depending on the mark length which is intended to be basically formed, (a) by lowering a strength of the irradiation light (for example, single pulse) when the short mark is formed than a strength of the irradiation light (for example, multi-pulse) when the long mark is formed, (b) by comparing pulse widths of the irradiation light when the short mark is formed with the pulse width of the irradiation light when the long mark is formed and shortening it more than the difference of the mark length of the short mark and the long mark, or (c) by changing both strength and the pulse width of these irradiation light depending on the mark length.
In this case, like the conventional record compensation method by which the position of the leading and the end of the irradiation light pulse are moved beforehand according to the length of the mark which intends to be formed and the mark is formed, a complex circuit like the programmable delay line is never needed to change the amount of the change and by the change of an optical pulse from the clock synchronization and the occurrence according to the mark length, compensation of the record as mentioned above can be achieved by using the strength switch function that the power controller of the optical disk drive has it essential, and performing an easy pulse width expansion and contraction operation. Therefore, high information record reliability can be obtained by improving the accuracy of the mark formed without greatly increasing a cost.
Even when the line record density, i.e., the record density in the mark length direction is different, the shift of the beginning position and the termination position of the mark is decreased depending on the mark length which intends to be formed further in the present invention, (axe2x80x2) a degree of lowering the strength is changed according to the record density in the mark length direction when the strength of the irradiation light when the short mark is formed like (a) is lower than strength of the irradiation light (for example multi-pulse) when the long mark is formed, or (bxe2x80x2) a degree by which the pulse width is shortened according to the record density in the mark length direction is changed, when pulse widths of the irradiation light when the short mark is formed like (b) are compared with the pulse width of the irradiation light when the long mark is formed and it shortens it more than the difference of the mark length of the short mark and the long mark, or (cxe2x80x2) by changing the degree of both strength and the pulse width of the irradiation light changes depending on the record density in the mark length direction when both strength and the pulse width of the irradiation light depend on the mark length like (c) to change it.
As described above, in the present invention, depending on the mark length which intends to be formed, for example, (a) strength of the irradiation light (for example single pulse) when the short mark is formed is lower than strength of the irradiation light (for example multi-pulse) when the long mark is formed, and the lowered degree is changed according to the record density in the mark length direction, (b) when pulse width of the irradiation light when the short mark is formed are compared with the pulse width of the irradiation light when the long mark is formed, it is shortened more than the difference of the mark length of the short mark and the long mark, and the shortened degree is changed according to the record density in the mark length direction, or (c) both strength of the irradiation light and the pulse width are changed according to the mark length, and the degree of the change depends on the record density in the mark length direction.
Therefore, according to the present invention, the shift of the edge position according to the length of the mark can be avoided, the amount of the shift at the beginning position of the mark can decrease even when the line record density, that is, the record density in the mark length direction is different, and can do the record compensation in which coexisting of accuracy and low-cost are enabled without complicating the hardware configuration.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.